Not Applicable
Not Applicable
1. Field of the Invention
This invention is in the field of devices used to connect pliable tubing to non-pliable mating devices or tubing.
2. Background Art
Many devices, especially in the medical field, utilize pliable tubing such as polymer tubing to conduct fluids, because of the flexibility of pliable tubing, which promotes ease of manipulation by the user. Specifically, in the field of cryosurgical probes, a refrigeration device such as a compressor typically delivers a cryogenic fluid for use in cooling a probe, which in turn is used to freeze target areas of biological tissue. The compressor is typically too large and heavy to be moved around by the surgeon in manipulating the probe. Therefore, flexible tubes may be used to conduct the cryogenic fluid from the compressor to the probe.
This requires that the polymer tubing be connected to the compressor at the proximal end, and to the probe at the distal end. These connections must be fluid tight, they must be reliable, and at least at the probe, they must be as compact as possible. Often, more than one polymer tube is required, for example, to provide a cryogen supply, a cryogen return, a saline solution supply, and one or more suction lines. When multiple polymer tubes are implemented, it is even more important for the connection assembly at the probe to be as compact as possible. Since the cryogenic fluid may be at a very low temperature and a very high pressure, the connection assembly must be able to provide a compact, reliable, fluid tight seal at very low temperature and high pressure.
Some known devices in the prior art attempt to seal these connections to polymer tubing by using epoxy or some other type of adhesive. These devices typically are difficult to apply and require some curing time, thereby adding to the expense of the assembly procedure.
Other known devices utilize one or more o-rings to accomplish a seal. These devices usually must be manufactured to precise tolerances to be effective, making them more expensive. Further, o-ring seals typically only seal over a relatively small portion of the area required for their implementation, making them subject to relatively high leakage for a given size.
Still other known devices attempt to accomplish a seal by swaging a metal member to the polymer tubing. Such swaging typically deforms the polymer tubing by a significant amount, thereby substantially altering the fluid flow characteristics of the tubing. Further, even when the metal member is swaged enough to significantly deform the polymer tube, the resulting joint is subject to substantial leakage, especially at high pressure and low temperature.
It would be beneficial to provide a compact sealing assembly which can join one or more pliable tubes to a rigid, or non-pliable, member without significant deformation of the pliable tube, without manufacturing or assembly problems, and without appreciable leakage at high pressures and cryogenic temperatures.
The present invention utilizes a compressible sealing wafer, which is compressed between two rigid components to result in a radially inward compression around one or more pliable tubes, to accomplish an hermetic seal around the pliable tubes. The compressible wafer seal has one or more holes therethrough for the passage of one or more pliable tubes, such as polymer tubes. The two rigid components define a cavity which is sized and shaped to axially compress the thickness of the wafer seal, while constraining the wafer seal to prevent it from expanding radially outwardly. This causes the wafer seal to tend to displace in an inward direction toward the centerlines of the holes of the seal, in turn exerting a radially inward pressure on the polymer tubes passing through the holes in the wafer seal. This exerts sufficient sealing pressure on the peripheries of the polymer tubes without appreciably deforming the tubes, since the wafer seal is itself pliable. The pliable tubes can have backing tubes inside, to provide support for the pliable tube in resisting the inward pressure of the wafer seal.
A bushing is used as one of the two rigid components, while the other rigid component can be a compressor manifold or a coupler at the handle of a cryoprobe. One or more through holes are provided in the bushing, for the passage of one or more polymer tubes. The bushing can have one or more swage tubes aligned with these through holes, with the polymer tubes passing through the swage tubes. A swage clamp can be provided to mate with the bushing, with swage holes in the swage clamp to swage the swage tubes lightly onto the polymer tubes, for the purpose of axially stabilizing the polymer tubes, preventing them from pulling loose from the compressor manifold or the cryoprobe coupler. The pliable tubes can have backing tubes inside, to provide support for the pliable tube in resisting the inward pressure of the swage tubes. In the preferred embodiment, the bushing is placed between the swage clamp and the manifold or the coupler, with the compressible wafer seal in a cavity between the bushing and the manifold or coupler. The cavity, which constrains the compressible wafer seal, can be formed either in the bushing, or in the manifold or coupler.
The novel features of this invention, as well as the invention itself, will be best understood from the attached drawings, taken along with the following description, in which similar reference characters refer to similar parts, and in which: